Ogre’s ruined spiny shrub (5)
I believe the answer is:
gorse
'spiny shrub' is the definition.
(I've seen this in another clue)
'ogre's ruined' is the wordplay.
'ruined' is an anagram indicator.
'ogres' anagrammed gives 'GORSE'.
(Other definitions for gorse that I've seen before include "Prickly moorland plant" , "Spiky shrub" , "Wild evergreen shrub with yellow flowers and sharp thorns" , "Ogres (anag.)" , "Welsh assembly" .)